The present disclosure relates to a method for processing a sample of biological material containing target cells and accompanying cells for extracting nucleic acids of the target cells and to a device for processing a sample of biological material containing target cells and accompanying cells for extracting nucleic acids of the target cells. The present disclosure concerns in particular the field of microfluidic systems, for example for so-called lab-on-a-chip devices.
In molecular diagnostics, there is often a need to detect pathogenic DNA or RNA in a sample. Pathogenic DNA or RNA refers to the DNA or RNA recovered from a pathogen, for example a virus or a microorganism, for example a bacterium or fungus. The sample is understood to mean in particular a blood sample, but in principle other liquid or liquefied patient samples, for example urine, stool, sputum, cerebrospinal fluid, lavage sample, a rinsed swab or a liquefied tissue sample, can also be meant, particularly when they contain blood or traces of blood. Symptoms in which this is relevant are, for example, urinary tract infections and sepsis. In the event of a suspected urinary tract infection, pathogens are to be detected from urine. In this case, a concentration of the pathogens can be very low, for example 103 to 107 per milliliter. In the event of a suspected sepsis, it is, for example, of interest to detect pathogens from blood and, if necessary, to determine resistances to certain antibiotics. Because of the concentration ratios between pathogens and leukocytes, for example 10 to 1000 per milliliter with respect to 106 to 107 per milliliter, there is in this case a very strong background of human DNA in the sample. Commercially available methods for selectively purifying pathogenic DNA from, for example, blood use, for example, chemical reagents in order to achieve firstly a selective lysis of human cells. Subsequently, the human nucleic acids are enzymatically digested. Pathogens are then isolated, for example by centrifugation and decanting of the supernatant. Such a method is, for example, disclosed in DE102005009479A1.
US 2010/0285578 A1 discloses devices and methods for recovering nucleic acids from biological samples.